Fluid power cylinders, such as pneumatic cylinders, are well known in the prior art. They are used to harness power from a fluid under pressure and to convert that power into motion.
A typical fluid power cylinder includes a cylindrical internal cavity which houses a movable piston. A rod is attached to the piston. The rod is moved selectively inward or outward by delivering fluid to the cavity on either side of the piston. Pneumatic cylinders typically have end caps that close each end of the cylindrical cavity. Each end cap includes a port into which air is delivered to move the piston and its attached rod.
When air is delivered under pressure to a first port of a pneumatic cylinder, air must be able to exhaust from the opposed second port. If air could not exhaust from the opposed side of the piston, the moving piston would eventually compress the air on the opposite side. When the pressure on both sides equalized, the piston would stop moving.
Pneumatic control valves are typically used to selectively deliver fluid to the ports in the end caps of the cylinder. In most cases, the same valve also controls exhausting the air from the opposed port as the piston moves. Many types of pneumatic control valves are known in the prior art.
A very useful type of pneumatic control valve design is one that uses a valve body and a detachable manifold. The valve body includes the control elements and other components necessary to route fluid between a plurality of openings, all of which are in a surface on the underside of the valve body. A mating manifold assembly includes openings which accept tubes or other conduits which are connected to the ports of the cylinder. The manifold also includes an opening that is connected to a source of compressed air. Often the manifold also includes openings through which the air exhausted from the cylinder is discharged.
The manifold also includes a plurality of internal passages which open at an outer face. The openings in the outer face of the manifold correspond to the openings in the underside of the valve body. The valve body is attached to the manifold so that the respective openings are in fluid communication, and the valve body operates to direct the flow of fluid through the manifold to control movement of the cylinder rod.
If the valve body experiences a malfunction, the body may be readily disconnected from the manifold and a substitute installed. This is accomplished without disconnecting the tubing connectors which supply compressed air and deliver and accept fluid from the ports of the cylinder. This construction saves considerable downtime when there is a malfunction.
Various manufactures of pneumatic control valves have standardized the openings in their respective valve bodies and manifolds so that any valve body of a particular type can be installed in place of a defective one. This standardization further reduces downtime because a user may keep a limited number of spare valve bodies on hand and still be able to repair a large number of valves.
In some applications it is desirable to mount a pneumatic control valve directly on a pneumatic cylinder. To accomplish this, the valve must be attached to the cylinder with fasteners. Unfortunately, some types of cylinders have end caps that cannot be drilled or otherwise modified to accept fasteners used for mounting a valve.
To overcome this problem, others have devised pneumatic control valves which may be directly mounted on a pneumatic cylinder through the threaded ports on the cylinder's end caps. Such a valve construction is shown in U.S. Pat. No. 4,651,625. This patent discloses a valve which uses a complex fastener fitting to connect the valve and attach it to the cylinder through the port. In addition to being complex and potentially costly, the construction disclosed in this patent presents the drawback that it does not lend itself to an interchangeable valve body construction. If there is a problem with the valve shown in this patent, the entire assembly must be removed from the cylinder and replaced.
Another cylinder mounted pneumatic control valve construction is shown in U.S. Pat. No. 3,233,523. This patent discloses a valve which includes a manifold mounted to the cylinder. The manifold is attached to the port using a fitting which is threaded at both ends. The problem with this approach is that the valve must be turned to install it on the fitting. This is cumbersome and time consuming. In addition, the valve may not be at the desired position when the fitting is fully tightened. This requires the valve to be over tightened on the fitting which could damage the seal and cause failures.
Another approach to mounting a pneumatic control valve on a cylinder is shown in U.S. Pat. No. 2,953,118. This design uses a threaded straight through fitting. The drawback of this design is that it would only be suitable for use with a very specialized valve body which is made to have ports that are in alignment with the fitting. Standardized types of valve bodies that are already in use in many applications could not be adapted to work with this construction.
Thus there exists the need for a port mounted fluid control valve construction that is adaptable to standardized types of removable pneumatic valve bodies, that is simpler to install and less expensive to manufacture.